New Zealand, one of the last countries successfully pursuing a zero-tolerance approach to the novel coronavirus, said Thursday it could open its borders for quarantine-free travel early next year. But only the vaccinated need apply.

The island nation sealed its borders about 1½ years ago and requires two-week stays in quarantine facilities for returning nationals. Only the odd American billionaire, some Pacific Islanders and residents of neighboring Australia have made it into what has been called “Fortress New Zealand” in recent times.

From early 2022, however, fully inoculated travelers from low-risk countries could skip quarantine, while vaccinated people coming from destinations New Zealand considers “medium-risk” might quarantine under more relaxed conditions.

Prime Minister Jacinda Ardern said in a Thursday speech that her center-left government remains committed to an “elimination” approach — crushing any small outbreaks as they arise — even as the country gradually opens up. In July, New Zealand officials popped the country’s quarantine-free travel bubble with Australia after just a few months, when an outbreak of the hyper-transmissible delta variant plunged millions of Australians into lockdown.

As the pandemic enters a new phase with variants such as delta emerging, the world is once again divided into starkly different approaches. Ardern has dismissed the approach of places such as highly vaccinated Britain, where Prime Minister Boris Johnson has said people must “learn to live with” the virus.

“Delta is a game changer in our risk calculation. It could be devastating if it took hold in New Zealand before we have high rates of vaccination,” Ardern told a gathering of scientists and media Thursday.

New Zealand has one of the lowest inoculation rates among developed economies. Only about 17 percent of its population of roughly 5 million is fully vaccinated. That compares with just over 50 percent in the United States.

New Zealand had effectively eliminated the virus with a strict lockdown early last year. Rare outbreaks are quickly stamped out with partial lockdowns and contact tracing.

For over a year, the country’s residents have enjoyed freedoms experienced only in recent months in the United States and Europe: mask-free outings and family gatherings, bustling restaurants, night clubs and crowded football stadiums.

Ardern’s popularity soared during the pandemic, although her Labour Party has ceded some ground in recent polls partly because of the slow vaccine rollout. Her government is mindful of preserving the relative normality New Zealanders have grown accustomed to, as it designs a cautious reopening to the world. That view has been cemented, she said, as restrictions snap back elsewhere after the hopeful start to the summer.

From early next year, New Zealand will consider several factors when determining how travelers from different destinations will be allowed in. These include the number of cases in a country, the prevalence of variants of concern, vaccination rates and New Zealand’s confidence in the country’s strategy for managing outbreaks.

Any loosening is likely to be conservative. Julia Albrecht, a tourism expert at the University of Otago, said she expects only a small number of “international visitors from selected countries in the first half of next year.”

“One of our problems is that our allies have let us down. Many countries that could have eliminated covid-19 either never tried or threw in the towel,” said epidemiologist David Skegg, who led a group of scientists advising the government on its plans.

New Zealand plans to test its travel initiative later this year, with local businesses and organizations that need to send staff abroad participating in a trial where returning employees quarantine at home, rather than in a hotel.

Wellington has been under increasing pressure to restart travel to revive industries including foreign education and tourism, previously a mainstay of the economy. Ardern stopped short Thursday of giving a target for the percentage of people who would need to be vaccinated before the country opens up, acknowledging that it is hard to make predictions when the virus “continues to change and mutate.”

The prime minister also announced an overhaul of New Zealand’s vaccine program, whose rollout has been constrained by supply issues, aimed at getting more adults at least partially vaccinated sooner. People will now wait six weeks between doses, up from three. The broad goal is to give every adult New Zealander the opportunity to be fully inoculated by December.

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